"KDE has released a first beta of the upcoming 4.7 release of the Plasma Desktop and Netbook workspaces, the KDE Applications and the KDE Frameworks, which is planned for July 27, 2011. With API, dependency and feature freezes in place, the KDE team's focus is now on fixing bugs and further polishing new and old functionality."

For my Radeon based setups, the open source driver runs much, much better on Compiz than kwin. I defiantly think there is a lot of room for performance improvements in kwin. The ATI drivers are much faster, but tend to be less stable. Kwin's feature set is useful enough that I tolerate the less than flawless performance.

You can always run KDE with compiz as the window manager.

Go to System Settings --> Default Applications --> Window Manager --> Use a different window manager

I think this requires you to install a helper application (it may be called kde-compiz) which will also install compiz itself as a dependency.

This is great on Arch Linux, which has rolling updates. In general Arch will pick up new stuff like this within a month or so. The Radeon drivers have already improved markedly twice this year, and the default (on Arch Linux anyway) has now switched from the classic mesa driver over to Gallium3D.